1. Field of the Invention
The present invention relates to agricultural vehicles such as combines, and, more particularly, to chopper knife assemblies used in straw choppers on such vehicles.
2. Description of the Related Art
An agricultural vehicle known as a “combine” is historically termed such because it combines multiple harvesting functions with a single harvesting unit, such as picking, threshing, separating and cleaning A combine includes a header which removes the crop from a field, and a feeder housing which transports the crop matter into a threshing rotor. The threshing rotor rotates within a perforated housing, which may be in the form of adjustable concaves, and performs a threshing operation on the crop to remove the grain. Once the grain is threshed it falls through perforations in the concaves onto a grain pan. From the grain pan the grain is cleaned using a cleaning system, and is then transported to a grain tank onboard the combine. The cleaning system includes a cleaning fan which blows air through oscillating sieves to discharge chaff and other debris toward the rear of the combine. Non-grain crop material such as straw from the threshing section proceeds through a straw chopper and out the rear of the combine. When the grain tank becomes full, the combine is positioned adjacent a vehicle into which the grain is to be unloaded, such as a semi-trailer, gravity box, straight truck, or the like; and an unloading system on the combine is actuated to transfer the grain into the vehicle.
More particularly, a rotary threshing or separating system includes one or more rotors which can extend axially (front to rear) or transversely within the body of the combine, and which are partially or fully surrounded by a perforated concave. The crop material is threshed and separated by the rotation of the rotor within the concave. Coarser non-grain crop material such as stalks and leaves are transported to the rear of the combine and discharged back to the field. The separated grain, together with some finer non-grain crop material such as chaff, dust, straw, and other crop residue are discharged through the concaves and fall onto the grain pan where they are transported to the cleaning system. Alternatively, the grain and finer non-grain crop material may also fall directly onto the cleaning system itself.
The cleaning system further separates the grain from non-grain crop material, and typically includes a fan directing an air flow stream upwardly and rearwardly through vertically arranged sieves which oscillate in a fore and aft manner. The air flow stream lifts and carries the lighter non-grain crop material towards the rear end of the combine for discharge to the field. Clean grain, being heavier, and larger pieces of non-grain crop material, which are not carried away by the air flow stream, fall onto a surface of an upper sieve (also known as a chaffer sieve) where some or all of the clean grain passes through to a lower sieve (also known as a cleaning sieve). Grain and non-grain crop material remaining on the upper and lower sieves are physically separated by the reciprocating action of the sieves as the material moves rearwardly. Any grain and/or non-grain crop material remaining on the top surface of the upper sieve are discharged at the rear of the combine. Grain falling through the lower sieve lands on a bottom pan of the cleaning system, where it is conveyed forwardly toward a clean grain auger.
The clean grain auger is positioned below the lower sieve, and receives clean grain from each sieve and from the bottom pan of the cleaning system. The clean grain auger then augers the clean grain laterally sideways to a clean grain elevator, which in turn conveys the clean grain to a grain tank onboard the combine.
The non-desirable crop material, known as “material other than grain” (MOG), can be processed prior to being discharged from the harvester. Typically, this processing involves cutting or “chopping” the MOG into small pieces that are easily handled and distributed. The MOG processing is often accomplished in a “straw chopper”, where the MOG is cut up or chopped by multiple knife assemblies mounted on a rapidly-turning rotary shaft. The smaller pieces are then discharged from the harvester and spread onto an agricultural field.
Over time, as the knives encounter the MOG during use, the working edge becomes dull. The knife is then typically removed from its mounting base, “flipped” 180 degrees, and re-secured. Thus, an unused and sharp working edge can be utilized until it, too becomes dull. The entire knife must then be replaced.
In order to achieve a finer and finer size of the MOG, more and more knives are used to process the material. It can be seen that there is therefore a considerable amount of time and labor needed to flip or change the knives.
Additionally, the large amount of torque needed for the bolts typically used to secure the knife to its base does not lend itself to easy installation or removal when service is needed.
The knives also encounter high centrifugal forces from being mounted to a rapidly-turning rotary shaft, as well as large shear and impact forces from contact with the MOG, or unintentional foreign material which may be entrained in the MOG.
What is needed in the art is a way to mount chopper knives in a manner that lends itself to quicker and easier assembly and disassembly, while at the same time providing the adequate strength needed to protect the knives from external forces.